Yes, the purpose is to pull up older posts that get cut off with the results or year limits.
Control Panel > Feature Settings > Search
DEFAULT SETTINGS:Search Method to Use: MySQL Full-Text
Maximum Search Date Range: 1 Year
Minimum Searchable Word Length: 3
Maximum Results from Search: 200
SETTINGS I RECOMMEND FOR OLDER SITES THAT HAVE A LOT OF USEFUL OLDER CONTENT:Search Method to Use: UBB.threads Internal
Maximum Search Date Range: 20 Years
Minimum Searchable Word Length: 3
Maximum Results from Search: 400
Since there is no "ALL" setting for "Maximum Search Date Range", setting it to something big, such as "20 Years," is an equivalent to that.
As a side note /slash/ recommendation --
In your php.ini (for PHP5.2.1+) your memory limit should be set at least to 128M
; Maximum amount of memory a script may consume
memory_limit = 128M
Your server really should be running on at least PHP 5.2.1 - for major stability and security enhancements
for more information, visit
http://php.net/releases/5_2_1.phpin PHP 5.2.0, the default was "16M"
prior to PHP 5.2.0, the default was "8M"
for more information, visit
http://php.net/memory-limit
